A system for the culture of mollusca especially oysters or for collecting mollusca larvae in a water stretch. This system is characterized by the presence of a source of gas under pressure, an inflatable and deflatable floatation device, a conduit connecting the gas source to the floatation device, a mechanism for the introduction of gas under pressure into the floatation device in order to inflate it and for the removal of gas from the floatation device in order to deflate it and fastenings associated with the floating device attaching the latter to a grid constituted of a three dimensional grid type arrangement of culture baskets or of a group of mollusca larvae collectors. The invention also relates to a method for the culture of mollusca, specially oysters in a water stretch, characterized by the following steps: (a) introducing mollusca strains in screen baskets thereby permitting the water to circulate freely through each basket; (b) disposing the baskets containing mollusca strings in a three dimensional grid type arrangement hereinafter called grid; (c) fixing an inflatable and deflatable gas floating device to the grid and varying the quantity of air into the floating device in such a way as to simply submerge the grid or allowing it to rest on the bottom of the water stretch.